class Solution {
public:
    bool containsNearbyDuplicate(vector<int>& nums, int k)
    {
        unordered_map<int, int > hash;
        for (int i = 0; i < nums.size(); i++)
        {
            if (hash.count(nums[i]) && abs(i - hash[nums[i]]) <= k)
            {
                return true;
            }
            hash[nums[i]] = i;

        }
        return false;
    }
};